Apparatus for the separation of air gases is generally supplied with air from at least one isothermal compressor provided with interstage refrigeration, in which the air is cooled by heat exchange with the refrigeration air.
The air leaving the compressor is itself cooled in a final cooler or in an air/water tower, generally associated with a water/nitrogen tower and/or a refrigeration group. This system, generally called "precooling", permits obtaining air at a relatively low temperature (about 15.degree. C.) before directing it toward a dryer, thereby limiting the load on this latter, the quantity of water contained in the air increasing exponentially with temperature. Such systems are described in "Current Alternatives by the Use of CFCs in Air Separation and Liquefaction Processes" by Walter F. Castle, Kryogenika 1996.
It is known to use the heat of the refrigerant of the compressor to reheat the regeneration gas, from JP 62-335691, JP 196772/94, and FR-2 686 405 and JP 7-144114.
However, the compressors used are isothermal compressors.
It is an object of the present invention to decrease the cost of an air separation unit.